1. Field of the Invention
The present invention relates generally to medical devices and procedures, and more particularly, relates to medical devices and procedures for removing thrombus or other tissue deposits from the cardiovascular system, natural or synthetic tubule or cavity found in the human body.
2. Description of the Prior Art
Procedures and apparatus have been developed for ease in removing various tissue. U.S. Pat. No. 4,790,813 issued to Kensey and U.S. Pat. No. 4,842,579 issued to Shiber describe techniques for the removal of plaque deposited in arteries by mechanical ablation using rotating cutting surfaces. These relatively traumatic approaches are directed to the treatment and removal of very hard substances.
In current medical procedures, thrombus and other tissue are often removed using a catheter such as is described in U.S. Pat. No. 4,328,811 issued to Fogarty. In this system, a surgical cutdown is performed to access the vessel and allow catheter entry and advancement to a point beyond the deposit. The balloon is inflated and the catheter is withdrawn pulling the tissue along with it.
Pressurized fluids have also been used in the past to flush undesirable substances from body cavities. U.S. Pat. No. 1,902,418 describes such a system for domesticated animals. The more modern approaches tend to use vacuum rather than gravity as the primary means for removal of the deposits or tissue and relatively low fluid pressures to cut into and fragment the substances to be removed.
U.S. Pat. No. 3,930,505 issued to Wallach describes a surgical apparatus for the removal of tissue from the eye of a patient. As with similar systems, Wallach uses a relatively low pressure jet of water (i.e. 15 to 3500 psi) to disintegrate the tissue, and a suction pump to perform the actual removal.
A similar approach applied to the cardiovascular system is discussed in U.S. Pat. No. 4,690,672 issued to Veltrup. Veltrup also provides a much lower pressure jet of water (i.e. less than 450 psi) to fragment deposits. As with Wallach, Veltrup uses a vacuum pump for evacuation of the fragments. The distal end of the Veltrup catheter is repositionable and requires manual entrapment of the deposits, or else the catheter jet must be moved into contact with the deposit in order to accomplish tissue fragmentation. The vacuum applied by the suction duct holds the tissue at its opening while a jet of water breaks up a solid structure at its mouth. This device is basically a suction tube which requires a vacuum to operate, but contains a distal jet aimed at the distal opening in order to reduce blockage of the opening.
The present invention achieves the removal of unwanted tissue by utilizing high-pressure fluid jets at the distal tip of a catheter to draw the tissue towards the catheter and cut or emulsify the tissue; the resulting slurry of tissue and liquid can then be removed through an exhaust lumen of the catheter, and the fluid jet(s) can provide energy to drive this exhaust. The present invention overcomes the disadvantages of the prior art systems by operating at higher pressures than those envisioned by Veltrup, thereby providing for entrainment of the thrombus or tissue into the fluid jet(s). In addition, the higher pressures produces a force which can be used to drive the fragmented tissue out of the catheter without using vacuum. The catheter can draw nearby thrombus or tissue towards the fluid jet(s), which then fragments it without requiring that the catheter be moved into direct contact or juxtaposition with the tissue. The high energy of the jet impinging on the opening to the evacuation lumen eliminates the need for a vacuum pump, as the fragmented debris is removed by the evacuation lumen as it is driven out with a driving force above atmospheric pressures.
According to the present invention, energy is added to the system via an extremely high pressure stream(s) of liquid, solution, suspension, or other fluid, such as saline solution, which is delivered to the distal end of the catheter via a high pressure tubing, which directs jet(s) of high velocity fluid at the opening of an exhaust lumen. This stream serves to dislodge thrombus deposits, entrain them into the jet, emulsify them, and drive them out of an exhaust lumen. Tissue or debris such as thrombus particles are attracted to the jet(s) due to the localized high velocity and resultant localized low pressure. Recirculation patterns and fluid entrainment bring the thrombus continually into close proximity of the jet(s). Once emulsified by the jet, the tissue can be removed through the exhaust lumen by flow generated as a result of stagnation pressure which is induced at the mouth of the exhaust lumen by conversion of kinetic energy to potential energy (i.e., pressure) of at least one fluid jet directed at and impinging on the lumen mouth. The pressure in the high pressure fluid tubing must be great enough to generate a high localized velocity, and hence, a low localized pressure necessary to entrain the surrounding thrombus or tissue. A high enough pressure to generate substantial stagnation pressure at the opening to the exhaust lumen is necessary to drive the exhaust flow. A pressure of at least 500 psi is needed for the high pressure fluid at the tip, and pressures of over 1000 psi will provide even better entrainment and stagnation pressures. The stagnation pressure formed at the mouth of the exhaust lumen serves to drive the fragmented thrombus or tissue out of the exhaust lumen. This pressure can typically be greater than one atmosphere, and therefore, provides a greater driving force for exhaust than can be accomplished by using a vacuum pump. Additional jets of lower energy may be directed radially outward to aid in removal of thrombus or tissue from the vessel wall, and provide a recirculation pattern which can bring fragmented tissue into contact with the jet(s) impinging on the exhaust lumen opening.
The procedure is practiced by percutaneously or intraoperatively entering the vascular system, tubule, or other cavity of the patient at a convenient location with a cannula. The catheter may be inserted either directly or over a previously positioned guide wire and advanced under fluoroscopy, angioscopy or ultrasound device to the site of the vascular occlusion, obstruction or tissue deposit. The exhaust lumen can permit the passage of an angioplasty dilation catheter, guidewire, angioscope, or intravascular ultrasound catheter for intravascular viewing. The lesion site may contain an aggregation of blood factors and cells, thrombus deposit, or other tissues which are normally identified by angiography or other diagnostic procedure. One or more balloons may be inflated to stabilize the distal end of the catheter and provide a degree of isolation of the area to be treated. An isolation balloon located proximal to the high pressure fluid jets can prohibit fragmented tissues from migrating proximally around the outside of the catheter shaft and immobilizing into a side branch of a blood vessel. An isolation. balloon distal to the high pressure fluid jets can prohibit immobilization distally. This may be of greater importance if immobilization of fragmented debris may generate unfavorable clinical sequelae. Thrombolytic drugs such as streptokinase, urokinase, or tPA, and other drugs may be delivered through the catheter along with the saline or separately to adjunctively aid in the treatment of the lesion. A balloon may also be located at the distal end of the catheter to provide the capability of dilation of the vessel, tubule, or cavity either prior to or following the thrombus or tissue ablation and removal.
The catheter described herein is a part of a system in the first embodiment (FIG. 1) which includes a high pressure fluid supply, the fluid being either sterile saline or other suitable physiological solution compatible with the site of catheter operation within the body. The high pressure of the fluid can be generated with a positive displacement pump, such as a piston pump, which can be made to operate with either pulsatile flow or with steady flow. The catheter and the piston pump can be sterile. A nonsterile motor and motor control system can be used to power the piston pump. Sterile saline and physiological solution available to radiological, cardiological and operative sites can be used as a source of fluid from the high pressure positive displacement pump. The high pressure fluid flow from the pump is supplied via a high pressure tube to the distal end of the catheter where at least one jet of fluid is directed toward the opening of an exhaust lumen. A metering device may also be a part of the system which includes the catheter and the high pressure fluid supply. A metering system can be utilized at the proximal end of the exhaust lumen to regulate the flow rate of the fragmented thrombus or tissue out of the catheter. The flow of fragmented tissue out of exhaust lumen can exceed the flow of high pressure fluid from the jet(s) which impinge on its distal opening. As a result, a metering device can be used to reduce the volumetric outflow rate of fragmented tissue such that it is equal to, or in balance with, the volumetric rate of high pressure fluid being supplied to the distal tip. This balance of flow would then insure that the fluid volumes within a blood vessel, tubule or body cavity is not being significantly altered during the thrombectomy or tissue removal procedure. The outlet flow rate of the tissue fragments can also be adjusted such that it is either greater than or less than the high pressure fluid supply rate, in order to either drain or expand the fluid volume within the vessel or cavity. The metering device can be any device with means of measuring the outlet flow rate and adjusting it to a desired magnitude. A roller (peristaltic) pump can be used as a metering device in this application. When used with a specific tubing and rotational speed, prescribed volumetric output of the fragmented tissue will be exhausted.
A manifold attaches to the proximal end of the catheter to provide leak-free access pathways for the high pressure fluid supply, the exhaust pathway for fragmented tissue to be delivered to a collection reservoir, the pathway for fluid (either gas or liquid) for inflation of balloon(s) at the distal end of the catheter (if desired), and the access port for introducing an auxiliary diagnostic or therapeutic device available to the physician. Such therapeutic devices may include a guidewire used to guide the catheter to its appropriate site in a vessel, tubule or cavity. A diagnostic device may include an ultrasound catheter or an angioscope. Contrast agents, thrombolytic drugs, or other drugs may also be delivered to the lesion site either using the exhaust lumen or the high pressure supply tube. A balloon inflation means can be connected to the manifold to deliver a gas or fluid to inflate a balloon(s) located at the distal end of the catheter. Such balloon(s) can serve to either reduce immobilization of fragmented tissue or for dilation of the lesion. The balloon inflation means can be a sterile syringe or other device available for inflation of angioplasty catheter balloons.
According to the second embodiment of the present invention (FIG. 3), there is provided a thrombectomy or tissue removal catheter having a manifold at the proximal end and having a distal end which enters percutaneously into a blood vessel, tubule, or cavity of the body in order to fragment thrombus or other tissue obstruction and remove the fragments out of the body. The saline or high pressure fluid enters the catheter manifold and is routed via a high pressure conduit such as a hypo tube or polyimide tube to the distal end of the catheter where it exits through at least one orifice, which forms one or more jet(s) of high pressure fluid which are directed at the opening of an exhaust lumen. The exhaust lumen carries the fragmented tissue from the distal end of the catheter to the manifold which is located outside the body. The high pressure tubing forms a loop at the distal tip with the plane of the loop being perpendicular to the axis of the catheter shaft. Holes drilled into the loop form the orifices which direct jets of saline in a proximal direction back towards the opening of the exhaust lumen. One or more of these jets provides the stagnation pressure at the opening of the exhaust lumen to drive a volumetric outflow of fragmented tissue, which can be greater than the flow rate of the high pressure saline. The stagnation pressure can be higher than one atmosphere, thereby generating a greater exhaust rate than can be accomplished by creating a vacuum at the proximal end of the exhaust lumen with a vacuum pump. The development of a stagnation pressure at the opening of the exhaust requires a pressure within the high pressure tubing at the distal end to be at least 500 psi with improved results occurring with pressures of over 1000 psi. In order to obtain significant entrainment of thrombus or tissue into the high velocity jet(s) as a result of their localized low pressure, it is necessary to operate the device with the pressure of the fluid in the high pressure tubing at the distal end, being at least 500 psi. Without high pressure, the amount of entrainment of surrounding tissue and thrombus, which moves into the jet for ablation, is minimal and the catheter would require direct contact of the jet or juxtaposition with the material to be fragmented. A distal pressure of over 1000 psi for the high pressure fluid provides improved entrainment of tissue into the jet for fragmentation. The formation of a loop in the distal portion of the high pressure tubing provides the catheter with the capability of following over a standard guidewire (which then would be located within the loop), and still maintaining unobstructed access to the thrombus or tissue entrained in a jet, as well as access for at least one jet unobstructed by the guidewire to impinge on the exhaust lumen and generate the stagnation pressure to drive tissue fragment exhaust. The guidewire can follow through the exhaust lumen of the catheter to efficiently utilize the available space and minimize the diameter of the catheter shaft. The distance between the orifice(s) and the entrance to the exhaust lumen is another important variable in determining the amount of stagnation pressure generated. A distance of one half to five millimeters will provide adequate stagnation pressure to drive exhaust, and still provide enough space for thrombus or tissue to become entrained for fragmentation. As this distance becomes greater, there is a tendency towards significantly less stagnation pressure; as the distance becomes smaller, little or no benefit is gained due to limited entrainment.
In the third embodiment of the invention (FIG. 8), there is provided a tissue removal catheter similar in every way to that of the second embodiment except that the orifice(s) are located a further distance away from the opening to the exhaust lumen. At a distance of greater than five millimeters, the jet spray pattern tends to fan out with much of the spray missing the exhaust lumen and also a great loss in its kinetic energy. Even though this device does not generate enough stagnation pressure to drive the exhaust flow, it still will be fully capable of entraining thrombus or tissue into the jet as long as the pressure within the high pressure tubing at the distal end is greater than 500 psi. The catheter, therefore, does not have to be brought into juxtaposition or contact with thrombus or tissue for it to fragment the tissue. The localized negative pressure will draw the thrombus or tissue into the jet. Exhaust can be accomplished in this case by applying a vacuum or suction as needed.
According to the fourth embodiment of the invention (FIG. 9), there is provided a catheter similar to that of the second embodiment except with the addition of the following feature which can add to its performance. This device provides additional radially directed jets of fluid to the distal end of the catheter. These additional jets are directed with radial component outwards in order to help dislodge the thrombus or tissues from the blood vessel, tubule, or cavity. The outward jets are of a lower velocity than the jets which direct fluid at the opening of the exhaust lumen. The lower velocity jet(s) will not damage the vessel wall or cause damage to the blood which they may contact. Approximately three jets will clean the perimeter of a vessel or tubule, and will set up a recirculation pattern where the fluid from the radial jets is directed to form a path leading toward the localized low pressure region of the high velocity jets directed at the opening of the exhaust lumen. This recirculation pattern helps to clean the vessel or tubule with greater efficiency.
According to the fifth embodiment of the invention (FIG. 14), there is provided a catheter similar to that of the first or fourth embodiment except that the following additional features have been added to help performance in specific applications. The catheter shaft tubing can be constructed of plastic with a dual lumen which can provide one lumen for exhaust in a manner similar to the second embodiment and a second lumen for carrying a fluid (either gas or fluid) for inflation of a balloon located on the distal end of the catheter. The balloon can be constructed of latex, silicone, polyurethane, or other elastic material and can serve to center the catheter, as well as isolate the distal end of the catheter so that fragments cannot migrate past the balloon. A balloon of this type could be located either proximal or distal to the fluid jets and exhaust lumen opening or in both locations. A dilation balloon constructed out of polyolefin, polyethylene, polyvinylchloride, polyethylene terethalate, or other high strength plastic could be similarly located at the distal end of the catheter. Such a balloon could be used to dilate a vessel lesion either before or after the catheter has removed tissue deposits such as thrombus. This catheter contains a separate tubing to carry the high pressure fluid from the manifold to the distal end to supply the high velocity jets.
According to the sixth embodiment of the invention (FIG. 15), there is provided a thrombus or tissue fragmentation catheter that does not remove the fragmented tissue. The device contains a high pressure fluid tube such as a hypo tube which delivers high pressure fluid to one or more orifices which direct jet(s) the fluid proximally toward the surface. The surface serves as a target for the jet(s), providing an element of safety to the catheter by prohibiting direct impingement of the jet on the wall of a blood vessel, tubule or duct. The jet has high velocity and low localized pressure due to the high fluid pressure of at least 500 psi in the high pressure tube. Therefore, the jet can both entrain tissue onto the jet, and break up the tissue or thrombus into fragments. No lumen is available in this catheter for exhaust of the fragments. The impingement surface can be made with an opening, which would allow for guidewire passage although it is not required. The distal end of the hypo tube can be made into a loop to provide for guidewire passage although it is not required. Fragments generated by this device can be allowed to remain in the vessel, tubule, or cavity, may embolize with blood flow, or may be washed out using other means.
According to the seventh embodiment of the invention, which applies to previous embodiments that contain an exhaust lumen, there is provided a catheter with a high pressure tube to deliver high pressure fluid from the proximal end of the catheter to the distal end where the fluid is directed by one or more orifices at high velocity onto the distal opening of an exhaust lumen. The pressure in the high pressure tubing at the distal end is at least 500 psi in order to effectively break up the thrombus or tissue deposit. A suction may be applied to the proximal end of the exhaust lumen with a vacuum pump to provide for removal of the fragmented thrombus or tissue, or a roller pump may be used to accomplish a similar effect. The pressure in the high pressure tubing at the distal end may be greater than 500 psi with improved tissue fragmentation occurring at pressures over 1000 psi. Entrainment of tissue such as thrombus into the localized low pressure region of the high velocity jet allows the device to operate effectively without requiring direct contact or juxtaposition of the catheter with neighboring tissue deposit. The distal end of the high pressure tube may form a small arc in order to direct the jet of high pressure fluid proximally toward the opening of the exhaust lumen or it may form a loop perpendicular to the axis of the catheter shaft in order to direct several jets of fluid rearwards. The loop allows the catheter to follow over a guidewire to reach the lesion site and to effectively fragment thrombus around the entire perimeter of the guidewire, vessel, tubule, or body cavity.